/*
  将下面异步代码使用 Promise 的方法改进
  尽量用看上去像同步代码的方式
  setTimeout(function () {
    var a = 'hello'
    setTimeout(function () {
      var b = 'lagou'
      setTimeout(function () {
        var c = 'I ♥ U'
        console.log(a + b +c)
      }, 10)
    }, 10)
  }, 10)
*/

var a = 'hello';
var b = 'lagou';
var c = 'I ♥ U';

let Interval = 10;

function wait(str, millisecond) {
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(str), millisecond)
  })
}

wait(a, Interval)
  .then(res => wait(res + b, Interval))
  .then(res => wait(res + c, Interval))
  .then(console.log)
